1. Field of Invention
The present invention relates to the technology of once-through boiler and the related devices, and more particularly to a method of detecting dryness of wet steam of a once-through steam injection boiler and a detecting apparatus therefor.
2. Description of Related Arts
Steam is an important secondary energy, and has been applied widely in industrial production and people's daily life. To further improve the management level of energy, the parameters such as steam dryness should be detected precisely and treated correspondingly.
The dryness of wet steam is an important quality parameter of water vapour. Ordinarily, we define the ratio of the mass of gas phase dry saturated vapour to the total mass of wet steam as the dryness of wet steam. In industrial production, real-time measuring and controlling the dryness of wet steam is necessary.
For example, in the end stages of vanes of a steam turbine, the dryness of steam affects the service life of the vanes of the steam turbine and the efficiency of the steam turbine greatly; on many occasions such as chemical industry, food processing, and pharmacy, the dryness of steam needs real-time detecting and controlling; in thermal oil extraction, the dryness of the high temperature wet steam injected into the oil layer has great effect on the economic efficiency of the oil extraction.
However, there is not an engineering measuring device for the dryness of wet steam at home and abroad, wherein the engineering measuring device is capable of real-time measuring, has high accuracy and long service life, and is cheap and reliable. Therefore researching and developing the measuring technology of the dryness of wet steam and the measuring apparatus therefor has practical meaning.
It is worth emphasizing that, steam stimulation is the leading process technology of heavy oil extraction, the dryness of steam is the main parameter of steam injection process, and increasing the dryness of stem in well bottom is the core question of increasing the economical efficiency of the thermal oil extraction. It is generally admitted that, the higher the dryness of the steam injected into the well is, the more efficiently the energy is utilized, and therefore the better the economic efficiency of the thermal oil extraction is.
Among the prior methods of measuring the dryness of wet steam, some people measure the dryness of the coagulated steam according to the energy conservation principle, others adopt chemical titration method (alkali concentration). According to the traditional boiler technology, detecting the dryness of the steam in the boiler adopts a special detecting method carried out periodically (generally once per hour). The special detecting method has defects that the steps are complicated, the detecting period is too long, the detecting can not be controlled automatically, and the detecting effect is hard to guarantee.
People thirst for a method of detecting dryness of wet steam of a once-through steam injection boiler and a detecting apparatus therefor, which have better technical effect.